Cytohistological Features of Spindle Cell Lipoma- A Case Report with Differential Diagnosis

Unusually Large Submucosal Mandibular Lipoma of Buccal Vestibule: a Case Report and Review of Literature

Despite being one of the most common mesenchymal benign tumors in the body, lipomas in the oral cavity constitute only 1-4% of all benign neoplasm. Buccal mucosa is the most common anatomic site within the oral cavity which is followed by tongue, lips, floor of the mouth, palate, vestibule, retromolar area and gingiva. The average tumor size ranges from 10 to 30mm. We present a rare case of unusually large sub-mucosal lipoma in lower buccal vestibule measuring about 52×29×22mm at its greatest dimension.

Spindle cell lipoma: clinicopathologic characterization of 40 cases

OBJECTIVE

In view of the existence of multifarious pathologic subtypes of spindle cell lipoma (SCL), which is easily misdiagnosed as other benign and malignant soft tissue tumors, we performed this study and aimed to better define the category of SCL.

METHODS

We collected and analyzed 40 cases of SCL with complete clinical and pathologic information from January 2010 to December 2018. Clinical and histopathologic analyses of SCL were performed, as well as immunohistochemical staining and fluorescence in situ hybridization (FISH) using probes for RB1 and MDM2, and the related literature was reviewed.

RESULTS

In 40 cases, the male to female ratio was 3.4:1, and the mean age was 54 years old. SCL of our study included six pathologic subtypes: classic (25/40), fibrous (4/40), myxoid (4/40), low-fat (3/40), pseudoangiomatous (2/40), and fat-rich (2/40) changes. Microscopically, SCL showed distinctive morphology, with uniform spindle cells and a variably adipocytic component. The spindle cells were bland in morphology, without prominent atypia or pleomorphism, set in a myxoid or fibrous matrix. Immunohistochemically, CD34 and vimentin were positive in spindle cells, and spindle cells of 6 cases also expressed S-100 protein. FISH analysis of 10 cases revealed that heterozygous deletion of RB1 was in six samples with chromosome 13 aberrations and MDM2 gene amplification was not detected in any cases. Surgical resection is considered as the primary treatment for SCL, as there was no any recurrence or metastasis in our cases after 2-105 months of follow-up.

CONCLUSIONS

SCL is a rare benign lipoma, and the proportion of spindle cells and adipocytic component varies, which may form various pathologic changes. The diagnosis needs to be combined with clinicopathologic features, immunophenotypes, and genetics. It has to be differentiated from mammary-type myofibroblastoma, cellular angiolipoma, solitary fibrous tumor, and myxoid liposarcoma.